Wow, surprised at first. But a little thought and clearly convective flow rate vs speed of sound in a fluid are vastly different. A bit like conduction charge speed in a metal vs signal speed in the same. And these sound waves can cross the convective zone with little dissipation?
Ah yes - core pushing out experiences a damping back-reaction, meanwhile the outflow towards the exterior enlarges the star somewhat, which requires conversion of thermal into increased gravitational potential energy. Cool (pun intended)!
Well in a sense, sans some interesting learning and relearning on the way, have come full cycle re original comment - it's all in equilibrium, so what the heck. But you will probably argue it's only quasi-equilibrium - there's a usually imperceptible dynamical balance driven from without, yes?